The present invention relates to a holder for electric devices, in particular, fluorescent lamps with two contact pins.
Tubular fluorescent lamps which are provided at the end with two contact pins are usually held in holders which have a so-called rotor for accommodating the contact pins disposed at the base of the lamp. The rotor is mounted rotatably on the remainder of the lamp holder, and has a slot which can be brought to correspond in alignment with an insertion slot of the holder housing. Moreover, there are arranged in the holder housing resilient contacts with which the contact pins come into contact when the relevant lamp base has been pushed into the holder and rotated by 90xc2x0 while the rotor is driven. Corresponding holders are widely employed. Both specialists and untrained users therefore mostly assume when changing fluorescent lamps that the fluorescent lamp held in the holders must firstly be rotated by 90xc2x0 about its longitudinal axis and then withdrawn from the holders.
The holder design is relatively expensive because of the rotatably mounted rotor. Attempts have therefore been made to go over to other types of holder design without rotatable elements, such as disclosed in the published draft of DIN IEC34B/554/CDV, Annex C. In addition to other types of holder design, a holder is presented which has an insertion slot which forks in the shape of a Y. Starting from an open-edged region, the insertion slot branches into two limbs at whose ends electric contacts are arranged for making contact with the contact pins of the lamp base. The spacing of electric contacts from the open-edged region of the insertion slot, which can be accessed by means of test fingers, is larger in this case than the spacing of the contact pins of the lamp base from one another. This is intended to ensure that no live parts are accessible from outside when the contact pins of the lamp base are inserted into the insertion slot of the holder. The two contact pins of the lamp base are interconnected via the incandescent filament present in the lamp. If only one of the contact pins touches a live contact, the other contact pin is therefore also live.
The safety lengths of the insertion slot which are thereby required prescribe a relatively large overall height of the holder. Furthermore, inserting and withdrawing the fluorescent lamps into and from the holder are performed by an unusual cycle of movements, and this can lead in some circumstances to damage to the holders and/or the lamp bases.
It is an object of the present invention to overcome the foregoing drawbacks and limitations.
It is a further object of the present invention to provide a lamp base which ensures the required shock protection and functions with as few parts as possible.
These objects, and others, are achieved by a holder for an electric device, in particular, a fluorescent lamp, with a two-pin base, comprising: an electrically insulating holder housing having at least one insertion slot on a side facing the base of the device to be held; electric contacts disposed in the holder housing; and latching members which act on a respective contact pin of the device to be held, the latching members being positioned in sections of the insertion slot in which the electric contacts are respectively disposed.
The holder according to the invention, has in its housing a branching insertion slot having two regions. One electric contact is arranged in each region. The electric contacts assigned to the regions extend into the insertion slot. Seen from the side of the insertion slot which is open-edged or opens outward, latching members are positioned in front of the electric contacts which apply a predetermined latching force. If a fluorescent lamp is inserted with its contact pins into the insertion slot in such a way that the contact pins are loaded toward the contacts, the latching members block the passage of the contact pins to the contacts. The latching members thus prevent contact from being made unintentionally with the contact pins, with the result that a contact pin still located outside the holder can be energized only when the contact pin already located in the holder overrides the latching force of the latching members positioned in front of the contact. The latching force is set so as to take account of requirements for electrical safety.
No rotor is required in the holder according to the invention, and so there is a corresponding simplification in the holder design. The holder housing can comprise a few parts (in the simplest case one or two) which accommodate and hold the contacts. If the holder housing is constructed in two parts, the part of the holder housing which faces the device, that is to say the lamp, can be constructed from a more heat-resistant plastic than the remaining part of the holder housing. Both the required heat resistance and cost effective production are achieved as a result, by virtue of the fact that it is possible for only the part of the holder facing the lamp to be constructed, to some extent, as a heat shield, and thus to be constructed from a relatively expensive plastic.
Although other designs are possible in principle, it is advantageous that the insertion slot has a branching point at which, preferably, a rectilinear section of the insertion slot intersects a circular section for accommodating the contact pins. The rectilinear insertion slot then extends from an open-edged point, opening toward the housing side, in a straight line over the side of the holder housing facing the device, intersecting in so doing the circular section and touching at the opposite point. This holder permits conventional handling of fluorescent lamps by firstly pushing the latter into the holder and then rotating them by 90xc2x0 about their longitudinal axis, in order to fasten and connect them. Withdrawal is performed in the opposite way.
In this design, the latching members are arranged next to the branching point at which the rectilinear part of the insertion slot crosses the circular part of the insertion slot. With the required reliability, they prevent a contact pin from touching a contact while the other contact pin is still located outside the holder. This is achieved without the need for the spacing of the contact from the opening of the insertion slot to be larger than the contact pin spacing. The construction of attractive holders which require little space and material is achieved as a result.
The latching members are preferably constructed in one piece on the holder. housing, it being possible for the latching members to be formed by a flexible housing section which constricts the insertion slot so far that the contact pin can be pushed through this region only with widening of the insertion slot. The resiliently flexible housing sections can be constructed both on one side and on both, mutually opposite, flanks of the insertion slot.
In an advantageous embodiment, a total of four latching members are provided which are respectively arranged in pairs next to the contact. Upon rotation of the device inserted into the holder, the contact pins run through the circular section of the insertion slot and in this way both come into contact in each case with a latching member. This produces a latching torque which is simultaneously distributed over both contact pins. The device is therefore cleanly guided by the holder when rotating about its longitudinal axis.
Independently of the number of latching members, the force required to override each latching member individually is greater than or equal to 10 N. This ensures the required electrical safety.
Latching members can be formed by a spiral spring section which is provided on the holder housing constructed from plastic and at whose free end a latching cam is seated which defines a constriction of the insertion slot. It is possible to provide the latching members on the holder housing with a device for supporting the contact pin in order to absorb the lateral forces acting on the contact pin and emanating from the latching cam, and to guide the contact pin on a clearly defined track in the shape of a circular arc, at least in the region of the latching member. This device can be formed by projections, ribs and other types of bearing surfaces.
The electric contacts are preferably mounted in the insertion slot in such a way that they are resiliently flexible toward its flank. If they are of rectilinear construction, simple contact shapes are ensured, in which case they occupy a relatively long slot region. The latching members ensure shock protection, nevertheless. Moreover, it is possible to provide the contacts with projections, bends or the like which cooperate in a latching fashion with the contact pins.
Further features and advantages of the invention will be apparent from the following description.